Drafting compass



Apri1'26, 1966 E. G BR o N 3,247,597 Y DRAFTING COMPASS Filed Aug. 21, 1963 I 2 Sheecs-Sheet 1 INVENTOR.

EDWARD G.BROWN BY ATTORNEYS April 26,- 1966 E. (5. BROWN pRAFTI'NG COMPASS 2 Sheets-Sheet z Filed Aug. 21. 1963 I I V,

ls ATTORNEYES United States Patent Filed Aug. 21, 1963, Ser. No. 303,603 3 Claims. (Cl. 33-153) This invention relates as indicated to a drafting compass and more particularly to a new and improved drafting compass more suitable than existing compasses of this general type for meeting the requirements of present drafting practices.

In present drafting practices, and particularly in the preparation of working drawings, it is becoming increasingly more common to eliminate the final step of inking and, instead, to make the necessary prints directly from the penciled drawings. Thus, the pencil lines in these drawings must be relatively dense and firm in order to produce satisfactory prints therefrom. It is accordingly a primary. object of the invention to provide a rugged, yet simple drafting compass for producing lines having the requisite noted characteristics.

It is a further object of the present invention to provide a drafting. compass having a novel means for adjusting the radius setting thereof.

Still another object of the invention is to provide a novel lead gripping structure the actuation of which can be accomplished by normal thumb or finger pressure without changing the grip on the compass from the normal operating position.

Yet another object of the invention is to provide a compass of such type wherein means are provided for adjustment of thefrictional resistance to movement of the hinged legs for varying the radius setting thereof.

These and other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully' described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a side elevational view, partially sectioned, of the compass embodying the invention;

FiG. 2 is a front elevational view, partially sectioned, of the compass;

FIG. 3 is a sectional view in enlarged form, taken on lines 33 of FIG. 1;

FIG. 4 is an' enlarged, sectional view of the hinged connectionfor the compass legs; and

FIG. 5 is an exploded perspective view showing more clearly the elements forming the hinge connection.

Referring now to the drawing, wherein like parts are designated by like reference characters, the drafting compass of the invention is generally indicated at 19 and comprises leg members 12 and 14 which are hinged adjacent the upper portions thereof by means to be described in more detail hereinbelow. The leg 12 is provided adjacent the lower end thereof with a laterally offset lug 16 having an opening extending therethrough for receiving a pointed center pin 18, the latter being held in place by means of set screw Ztireceivable in a tapped opening in the lug member.

The leg member ld-is provided adjacent the lower end thereof with a similar laterally offset lug member 22 having an opening through which extends a leadgripping collet assembly to be described in more detail hereinbelow for gripping or clamping an elongated lead Patented Apr. .26, T956 piece L which extends outwardly of the leg 14 in the usual operative manner. The lug 22 also serves as a limit or stop for maintaining the adjacent sides of the legs 12 and 14 in spaced relationship so as not to contact the lead gripping and receiving assembly disposed therebetween. The leg 14 is provided at the opposite upper end thereof with a threaded extension 24 adapted threadedly to receive a centrally bored operating knob 26 as shown in FIGURE 2. A spacer sleeve 28 is disposed around the extension 24 at the juncture thereof with the leg 14 for spacing the operating knob 26 from the leg 14 to facilitate grasping of the knob. As can be clearly seen in FIG. 2, the knob 26. is relatively large in diameter, approximating an inch, for example, to further facilitate grasping thereof andsimultaneous adjustment of the radius setting means, to be described hereinbelow.

Referring now to the lead gripping collet assembly shown in detail in FIGURE 3, thevlower end of leg 14 is provided with a tapered surface 32 adapted to be engaged by a similarly tapered shoulder 34 formed incoliet 36 adjacent the lower end thereof. The opposite end of collet 36 is threadedly secured to a tube member- 38, the collet 36 and tube 1nember-38 forming a relatively long cylindrical receptacle for receiving the elongated lead L of the type used, e.g., in .draftingpencils, approximately five inches in length. Referring for a moment to FIGURE 2, the, tube 38 extends through an opening in the upper end of leg 14 and is telescoped within and axially movable relative to the leg extension 24. The tube 38 has mounted on the: opposite end thereof by any suitable means a push button actuator 39 which is freely movable in the. bore of the knob 26 and partially extends outwardly thereof. A spacer sleeve 49 is telescoped loosely around the tube .38 and, collet 36 and the bottom thereof engages the offset lug portion 22 of leg 14. The tube 38 is provided with a fixed collar 42 for engagement with the upper convolution of a coil spring 44, the lower. convolution of whichis adapted to contact the upper end of the spacer sleeve 44) thereby biasing the tube 38 vertically upwardly. Under the bias of spring 44, the tapered surface 34 of the collet 36 is forced into engagement with the tapered opening 32 formed in the bottom of the leg 14 whereby the collet effectively grips or clamps the lead Lin operative position.

It will be seen that when the tube 38 and collet 36 threadedly connected thereto are moved vertically outwardly through actuation of the push buttton 3tlagainst the bias of spring 44, thetapered surface 34 of collet 36 will disengage the complementary tapered surface 32 of the leg 14 whereby the gripping pressure on the lead L will be released, thus freeing the lead L for sharpening, repositioning or the like. It should be noted that the lead can be released While the operatoris gripping the drafting compass in its operative position merely by depressing the push button 30 vwith the thumb or forefinger. As will be evident, as soon as the pressure on push button 30 is released, the spring 44, acting against collar 42 of tube 38, will force the latterupwardly. whereby the collet 36 will be moved to the lead gripping position above described.

Referring now to FIGS. 4 and 5 which more clearly illustrate the manner in which legs 12 and 14 are hingedly connected, legs 12 and 14 are provided with openings 46 and 48, respectively, for receiving a preferably nylon pivot bushing 50 having an annular shoulder or flange engageable with the adjacent surface of the leg 14. The legs 12 and 14 are spaced by means of an apertured friction washer 52 which also fits around the bushing 50. A bolt 54 is provided having a threaded ste-m portion 56 which extends through the bushing 50 and washer 85 for assembling legs 12 and 14 in hinged relationship, a self-locking nut 58 being threadedly mounted on the outer end of the threaded stem 56 to effect such connection. A dished, axially compressible pressure disc 59 is disposed between the beveled head of the bolt 54 and the leg 12, the disc 59 having a peripheral edge engageable with the outer surface of the leg 12 for variably adjusting the frictional resistance to movement of the legs 12 and 14.

As clearly seen in the exploded FIG. view, the opening 46 in the leg 12 is provided with serrations whereby the nylon bushing 50 is adapted to be force fitted therethrough so as to prevent relative movement between the bushing 50 and such leg 12. The force fitting effects the imprinting of the serrations into the exterior, smooth surface of the nylon bushin 50. The opening 48 of the leg 14 is smooth so as to accommodate rotation thereof on the bushing 50.

It will thus be seen that the resistance to movement of the legs 12 and 14 can be quickly and effectively ad justed merely through rotation of the bolt 54 which effects a tightening of the nut 58 thereon. The bolt 54 is in the form shown provided with a slot for receiving a suitable adjusting tool such as a screw driver. Such tightening of the nut 58 will effectively increase the clamping of the legs 12 and 14 against the friction washer 52 under the increased pressure exerted by the pressure disc 59 thereby stiffening the hinge joint. Similarly, a loosening of the nut 58 will decrease the clamping pressure on the legs 12 and 14 thereby increasing the ease in which the leg 14 can be moved relative to the leg 12.

Referring now to the means for varying the radius setting of the legs 12 and 14, a rack 60 is loosely pivotally mounted on leg 12 by means of screw 62 which is threadedly received in a tapped opening in the leg 12. Referring to FIG. 1, the rack 60 is adapted to engage a pinion 64 which is carried 'by a pinion shaft 66 which extends through an opening therefor in the leg 14, a bearing sleeve 68 being disposed around the pinion shaft 66. The pinion shaft 66 and pinion 64 carried thereby are rotated by means of a micro-adjustment knob 70 which is nonrotatably mounted on the pinion shaft 66 by means of set screws 72.

The rack 60 is maintained in engagement with the pinion 64 by means of a guide assembly generally indicated at 74, such assembly comprising an L-shape cover member 76 provided with a pair of threaded openings through the upper portion thereof, there being but one such opening shown in FIGURE 1, for threadedly receiving bolts 78 which also extend through openings in a vertically extending guide member 80. The depending leg portion 82 of the cover member 76 serves to space the rack 60 from the leg 14 and such leg portion is mounted adjacent its lower end on pinion shaft 66 for similarly spacing the pinion 64 from the leg 14. The guide member 80 is similarly mounted adjacent its lower end on the pinion shaft 66. The guide member 80 and cover 76 when assembled thus form a channel for receiving rack 60 and pinion 64, the channel of course being dimensioned to accommodate reciprocation of rack 60 and rotation of pinion 64 with little or no frictional resistance but yet maintain at all times the rack 60 in contact with the freely rotatablepinion 64.

The radius setting of the legs 12 and 14 can be effected in two ways: through rotation of the micro-adjustment knob 70 which will move the rack 60 responsive to rotation of the pinion 64; or by merely grasping the legs 12 and 14 and moving the same either toward or away from each other as desired. When adjusting the radius setting in the last described manner, the knob 70 will of course rotate as pinion 64 is rotated responsive to 4 movement of the rack 66. It should be noted that if the radius setting is desired to be changed while the compass is being gripped in its operative position, the operator can, without changing the grip, merely reach downwardly and rotate the knob 70 in the desired direction to either increase or decrease the radius setting.

It should now be apparent that applicant has provided a novel drafting compass which is ruggedly built and which is extremely convenient to use. The lead is controlled from a point at the upper end of the compass by means of push button 30, so that the lead may be extended while the operator is gripping the compass in the operative position. As above described, the radius setting can also be effected without changing the operating grip on the compass. The frictional resistance to movement of the legs 12 and 14 can easily and quickly be adjusted by tightening or loosening the clamping of the legs 12 and 14 at the hinge joint thereof, through the simple adjustment of the bolt 54.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A drafting compass comprising a pair of legs pivotally frictionally interconnected adjacent one end thereof, a spherical knob mounted on the end of one said leg adjacent such pivotal connection for manipulating said compass, marking lead gripping means on said one leg adapted normally releasably to grip a lead extending beyond and disposed parallel to said one leg, control means for said gripping means projecting through said knob operable to deactivate said gripping means to release such lead, and a pointed center pin mounted on the other said leg and extending beyond the end thereof.

2. The compass of claim 1, wherein the pivotal connection of said legs includes a nylon bushing nonrotatably secured in an opening in one leg, a headed bolt passing through said bushing into threaded engagement with nut means to secure said legs together for relative pivotal movement and adjustment, and an axially compressible disc having a peripheral surface in resilient engagement with said one leg.

3. The compass of claim 1, including micro-adjustment means comprising a rack pivotally mounted on one leg intermediate the ends of the latter, a pinion rotatably mounted on the other said leg, means holding said pinion in operative engagement with said rack, and a knob operatively connected with said pinion to turn the same.

References Cited by the Examiner UNITED STATES PATENTS 539,759 5/1895 Starrett et al. 33--153 613,814 11/1898 Benes 33153 1,465,746 8/ 1923 Turkovich 33152 2,187,519 1/1940 Meilner 33152 2,364,806 12/1944 Nash 33-153 2,650,845 9/1953 Dalley 287-101 2,828,668 4/1958 De Angelis. 3,042,961 7/ 1962 Tieri 16168 X FOREIGN PATENTS 954,799 6/ 1949 France. 931,131 8/1955 Germany.

9,440 1960 Great Britain. 873,525 7/ 1961 Great Britain. 501,177 11/1954 Italy.

ISAAC LISANN, Primary Examiner.

ROBERT B. HULL, Examiner. 

1. A DRAFTING COMPASS COMPRISING A PAIR OF LEGS PIVOTALLY FRICTIONALLY INTERCONNECTED ADJACENT ONE END THEREOF, A SPHERICAL KNOB MOUNTED ON THE END OF ONE SAID LEG ADJACENT SUCH PIVOTAL CONNECTION FOR MANIPULATING SAID COMPASS, MARKING LEAD GRIPPING MEANS ON SAID ONE LEG ADAPTED NORMALLY RELEASABLY TO GRIP A LEAD EXTENDING BEYOND AND DISPOSED PARALLEL TO SAID ONE LEG, CONTROL MEANS FOR SAID GRIPPING MEANS PROJECTING THROUGH SAID KNOB OPERABLE TO DEACTIVATE SAID GRIPPING MEANS TO RELEASE SUCH LEAD, AND A POINTED CENTER PIN MOUNTED ON THE OTHER SAID LEG AND EXTENDING BEYOND THE END THEREOF. 